This invention relates to powered rotary lawn mowers. More particularly, the invention pertains to rotary lawn mowers which can perform a mulching or recycling function whereby each blade of grass is cut multiple times during one pass of the mower. The objective is to cut the grass clippings small enough to be deposited deep into the lawn in as direct manner as possible where they can decompose without interfering with healthy lawn growth.
Mulching lawn mowers, also called "recyclers", are well known in the art. Existing mulching mowers are designed to cut and re-cut the grass blades of the lawn within a completely enclosed cutting chamber which surrounds the mower blade. This multiple recutting of clippings is repeated in a haphazard manner until the clippings simply fall or are partially assisted back onto the lawn beneath the chamber. During times of robust lawn growth and wet conditions, this method of cutting grass blades and recutting of clippings will produce a compound build-up of clippings inside the cutting chamber to the point where the mower will clog and/or discharge unsightly clumps or stripes of clippings onto the finished lawn. The build-up of a dense clipping circulation leads to the formation of deposits around the inside walls of the cutting chamber which will alter the shape of the chamber, thereby impairing its function. One consequence of this clipping density build-up and effective chamber distortion is that the mower engine must work harder to cut and discharge the clippings to the point that the engine may stall.
Prior art mulching mowers are also deficient in their ability to bury the clippings deep into the lawn where they can decompose and supply nutrients. Clippings which are deposited at or near the surface of the finished lawn are unsightly and impede transmission of the sunlight needed for healthy growth. A primary obstacle to clipping penetration in the mulching process is that grass blades act as a filter over the soil. The clippings must pass through the layers of upright blades of grass to reach the preferred resting destination at or near the soil. To overcome this obstacle, the clippings have to be small enough to pass this filter. They also need to be directed downwardly at or near a right angle to the filter layer and with sufficient velocity, especially in wet conditions, to free themselves from the uncut grass blades. Prior art mulching mowers have achieved poor results in this area.
What is needed, then, is a mulching lawn mower which consistently produces small grass clippings without fouling or clogging the cutting chamber of the mower and which discharges the clippings into the lawn in a manner which causes them to be deposited at or near the soil